»» We have no disclosures. There is limited data available for evaluating the progression to arthritis following arthroscopic anterior stabilization. Previous work reports rates between 8 and 22% of the patient population, but this varies based on surgical procedure. Risk factors identified previously include older age, recurrent instability events prior to stabilization. Regarding posterior shoulder instability, this accounts for 10% of all shoulder instability cases. But there is no available data evaluating progression to arthritis. Therefore the purpose of our study was to assess progression to and risk factors for arthritis in two different young patient populations undergoing arthroscopic shoulder stabilization. We performed a retrospective review of active-duty service members who underwent arthroscopic stabilization for shoulder instability from 2004 to 2016 in the military healthcare system, MHS. Our inclusion criteria were index surgery in MHS, unidirectional instability, the presence of radiographs and a minimum of 4-year follow-up. We had two distinct cohorts that were analyzed independently, an anterior instability group and posterior instability group. The variables included patient demographics and surgical characteristics. Our outcome of interest was glenohumeral arthritis as defined by the Samuelson and Prieto classification. Final follow-up was defined as the final encounter within our closed healthcare system. The incidence of glenohumeral arthritis was defined as 1,000 person-years per each cohort. And we identified 95% confidence intervals based on the Poisson distribution. For the anterior cohort, Cox regression model analyses were performed to identify risk factors associated with progression to arthritis. For the overall cohort, the patients were young with a mean age less than 25 and mostly male. There were 23 anterior and 14 posterior shoulder instability stabilizations that developed arthritis. Looking at the anterior instability group, 8% of the patients developed arthritis over median follow-up time period of 8.9 years. And for the posterior instability group, 12.7% of the patients developed arthritis over median follow-up time period of 8.1 years. On Cox regression model analysis, the risk factors for anterior progression to glenohumeral arthritis were older age at index surgery, number of anchors used at index surgery and revision surgery. Revision surgery was the strongest predictor for the development of arthritis. Regarding our posterior group, we did not identify any significant characteristics associated with the progression to arthritis. However, older patients did have almost two times the risk for the development of arthritis. However, this was not statistically significant. The effect size though did trend towards significance and may be clinically significant. We then compared our anterior cohort to work previously published in AJSM in 2004. Bouscaret et al. identified factors associated with arthritis after anterior shoulder stabilization procedures. This cohort was mostly athletes at 87% and civilian. Their mean age was 31.9. In this cohort, 9% of the patients developed arthritis over a follow-up period of 3.3 years for those that had anterior stabilization procedures done arthroscopically. Their risk factors were older age at initial dislocation event and surgery, dislocation number and longer follow-up. Compared to our cohort, which is all active duty service members slightly younger with a mean age of 22.7 for the anterior group, there was an 8% which is similar to 9% rate of development to arthritis over a longer follow-up period. Our risk factors were older age at the time of surgery, anchor number and revision surgery. Therefore these results may advocate for early surgical intervention for younger patients presenting with anterior shoulder instability. Our posterior group, 12.7, developed arthritis. We didn't identify any statistically associated risk factors with arthritis. But this may be due to our low event number which potentially limited our ability to control for confounding and limited our statistical analyses. Therefore formal analysis in a larger cohort may help guide clinical decision-making and chronicity of treatment. In conclusion, in a young high-demand patient population the rate of arthritis is low for both anterior and posterior shoulder instability groups. For anterior shoulder instability, revision surgery is the strongest predictor of arthritis followed by older age and anchor number. Thank you.

limited data

arthroscopic shoulder stabilization

anterior instability

posterior instability

risk factors